MUSCLE PHYSIOLOGY Flashcards
what are the 3 energy systems
- phosphagen system
- glycolytic
- oxidative
which energy system is used when
the phosphagen system and glycolytic system are used in intermittent bouts of high intensity exercise where oxygen is not needed and the regeneration of ATP is required rapidly
eg: sprinting
-the oxidative system kicks in in endurance training of lower intensity
in ascending order list the systems according to their rate of ATP production
- oxidative
- slow glycolytic
- fast glycolytic
- phosphagen
what are the adaptions that occur to anaerobic training
- neural
- muscular
- endocrine
- cardiovascular
what are the neural adaptations that occur
- increased firing rate of neurons
- synchronization of the neural discharge
- increased agonist recruitment
- decreased inhibitory mechanisms
- the motor cortex activity increases and so there is increased recruitment of motor units
when do the neural adaptations occur
6-10 weeks into the training programme; before any muscular adaptations can occur
what is the size principle
principle by which motor units are recruited. done in an ascending fashion from low to high threshold motor units ie; according their the recruitment threshold and force production
- the low threshold motor units that recruit slow twitch type 1 muscle fibres are recruited first and then as the exercise load increases; the high threshold motor units containing fast twitch, type II muscle fibres are recruited
how would an athlete gain maximal force production
by activating all motor units so as to recruit all available muscle fibres
what is selective recruitment
this is when the size principle is overruled and the high threshold motor units are activated out of turn ie; before the low threshold motor units.
- this is neccesary in times where great force production is required rapidly ie; sprinting or weight lifting
how is the neuromuscular junction adapted with training
- increased CSA of the synapses
- increased terminal branching and synapse dispersion
- increased ach receptors in the motor end plate
how are the muscular reflexes adapted with training
- the stretch reflex and muscle spindle increase in force production with training and so they are able to generate more force in a contraction without any additional energy required to generate that force
what is the main muscular adaptation that occurs with exercise
hypertrophy: enlargement in the CSA of muscle fibres
what does hypertrophy involve
- increase in actin and myosin production
- increase in the number of myofibrils in the fibre
how does training induced actin and myosin synthesis differ between trained and untrained individuals
the increase in synthesis of these 2 proteins post exercise remains elevated for longer in untrained individuals
-this is why untrained individuals experience more rapid exercise induced muscle hypertrophy
how is the hypertrophy process regulated
by the lysosome
explain the steps of hypertrophy
- contraction in the muscle activates a mechanoreceptor
- this activates enzymes producing PA so PA levels increase and can bind to mTOR.
- this also activates the enzyme producing erk so that erk can inhibit the action of TSC-2 on rheb.
- so rheb can also now bind to mTOR
- active mTOR stimulates protein synthesis
- which leads to hypertrophy
what is the function of satellite cells
-they are undifferentiated cells that can be activated during resistance training to proliferate and differentiate into myocytes that will fuse to existing myofibres. this means they donate extra nuclei to the fibres which allows for increased protein synthesis and thus; additional fibrils to be made.
-they also function in muscle injury where they are activated by the damage and proliferate and migrate to the damage site. then they will differentiate into myoblasts that fuse to form myotubes that further fuse to form myofibrils =replace the damaged tissue
what is hyperplasia
the increase in the number of fibres by longitudinal fibre splitting
when is hyperplasia seen in humans
amongst steroid users. because they reach an upper limit in fibre size they then experience hyperplasia
what is the difference in fibre size change between type 1 and 11 fibres
type 2 fibres have a greater capacity to increase in size than type 1 and so those born with more type 2 fibres are going to be able to increase their muscle mass by more
fibre type transitions with exercise
see a transition from type 11x to 11a ie; to a more oxidative kind
-cannot change the amount of type 1 and 11 fibres you have
what happens to the pennate angle with exercise
this is the angle that a muscle projects from its tendon at.
-this angle seen to increase with training
-this increase allows for greater force production and greater increase in CSA of the fibres
